Method and apparatus for expanding clay granules

ABSTRACT

A method and apparatus for expanding clay granules with the steps of producing a hot gas stream in a combustion chamber as an axially streaming, swirling gas stream, introducing the axially streaming, swirling gas stream into a treatment chamber having a narrowing bottom portion as an ascending gas stream which does not fill the entire cross section of the chamber, and introducing a charge of granules into the treatment chamber to be carried along by the ascending gas stream, the granules being permitted to leave the gas stream, fall back under the effect of gravity and recirculate until all of the granules of the charge are completely expanded. The swirling gas stream is tangentially fed into the combustion chamber through slots in the vicinity of the bottom portion thereof, and fuel is atomized into the gas stream by a burner having nozzles and arranged centrally in the combustion chamber at the bottom thereof. The interior of the combustion chamber may be partitioned by two walls, the gas flowing upwardly around one wall and downwardly between the walls before passing into the central area of the combustion chamber.

[ NOV. 28, 1972 METHOD AND APPARATUS FOR frimary Examiner-John J. Camby Attomey-Spencer & Kaye EXPANDING CLAY GRANULES [72] Inventors: Heinz Dennert, Trosdorferweg 6, D-

[57] ABSTRACT A method and apparatus for expanding clay granules 8602 Bischberg; Hans Veit Dennert,

with the steps of producing a hot gas stream in a combustion chamber as an axially streaming, swirling gas stream, introducing the axially streaming, swirling gas stream into a treatment chamber having a narrowing ttom portion as an ascending gas stream which does not fill the entire cross section of the chamber, and introducing a charge of granules into the treatment chamber to be carried along by the ascending gas stream, the granules being permitted to leave the gas stream, fall back under the effect of gravity and recirculate until all of the granules of the charge are completely expanded. The swirling gas stream is tangentially fed into the combustion chamber through ots in the vicinity of the bottom portion thereof, and fuel is atomized into the gas stream by a burner having 1 nozzles and arranged centrally in the combustion chamber at the bottom thereof. The interior of the combustion chamber may be partitioned by two walls, the gas flowing upwardly around one wall and downwardly between the walls before passing into the central area of the combustion chamber.

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Heinz Dgnnert Hons VeIi Dennert PATENTEDN I 3.704.010

SHEETEUFS INVENTURS. 'Hemz De nnert Hons Veir Dennen ATTORNEYS.

PATENTED NOV 2 8 1972 SHEET 3 [IF 3 l '\\"EI\T-ORS. Heinz Dennerr Hons Veit Dennert BY: fi' X ATTORNEYS.

METHOD AND APPARATUS FOR EXPANDING CLAY GRANULES BACKGROUND OF THE INVENTION The present invention relates to an improved method for expanding clay granules in a circulation flow, and apparatus for accomplishing this novel method.

A method for expanding clay granules in a circulation flow is disclosed in German printed application No. 1,199,176, corresponding to US. Pat. No. 3,216,125 issued Nov. 9th, 1965. This method is accomplished in charges and is carried out in the following manner: Hot treatment gas in the form of a free jet is introduced to a treatment chamber, the cross section of the free jet being only a fraction of the chamber cross section. Approximately in the area where the free jet enters the treatment chamber, the charge of the clay granules to be expanded is introduced into the hot gas stream. These granules are carried along by the gas stream to a certain height at which the upward surge of the gas stream which decreases with the height of the chamber no longer suffices to carry the granules. Since with the decreasing upward surge there also occurs a certain dispersion of the originally substantially closed gas stream, the granules leave the gas stream. The gas is extracted at the head of the chamber outside of the stream, whereas the granules fall back to the point of entrance of the gas stream and are again carried upwardly along the gas stream. The granules perform this cycle until the entire charge is expanded and then discharged.

Before discussing the present invention in detail, the method disclosed in U.S. Pat. No. 2,435,927 will be explained. The invention of this patent relates to the drying of materials and not to the expanding of clay granules, but the technique employed is of certain interest in connection with the present invention.

The treatment chamber in the above-mentioned patent consists of a weak, conical jacket with a stronger conical bottom portion. A stream of the material to be treated is thrown into the bottom portion by a centrifugal machine which is called the thrower, and a hot gas stream is additionally introduced. The gas stream encloses the stream of the material, but does not carry it along. Above the bottom portion, warm gas that is, gas of a lesser temperature than the hot gas is brought tangentially into the jacket above the bottom portion thereof, which warm gas is discharged again from the separator connected to the treatment chamber. The treatment chamber is under a certain subatmospheric pressure which is produced by a suction blower.

Treatment material and the stream of hot gas initially flow parallel to one another through structure in the form of cylinders. They are enclosed by a jacket of warm gas which, due to its tangential introduction and due to the induced draft present in the chamber, performs helical movements. This warm gas initially does not participate in the actual treatment process. After passing through a certain length of the chamber, the

upward surge of treatment material and gas decreases and they disperse. This results in mixing with the helically moved warm gas. On its further path, the treated material is moved in a helical line until it is sucked out at the head of the chamber. This occurs only, however, for the finest and dryest particles.

The heavy particles, which are not carried along by the helical movement of the, now, mixed treatment gas, either float in the mixing zone until they are completely dried or they fall through the helical gas flow with greater or lesser speed. Once the heavy particles become dry enough, the gas again carries them along. If they are still too heavy, however, they fall to the bottom, are there discharged and are reintroduced into the treatment chamber by the throwing device. This is a process in which the intake and discharge of the treatment material are continuous.

The principle of the circulation flow, when reduced to practice, resulted in some, quite considerable, problems. It was found that fault free expansion of a charge requires a substantially homogeneous temperature distribution across the cross section of the free jet. This produced one of the problems. An attempt to produce the free jet by a single, correspondingly large burner did not bring the desired result. It was not possible to produce the required temperature homogeneity of the free jet together with the necessary dependability. This was overcome by inserting below the treatment chamber a combustion chamber with a plurality of nozzles whose combustion gas streams combine into a homogeneous combustion gas due to turbulence. The combustion gas is introduced into the combustion chamber as a free jet through a nozzle or aperture. Thus, the problem of inhomogeneous temperature distribution was solved. 7

However, another phenomenon occurred. A free jet may be defined as not having a confining cylinder and not having a pressure distribution which is uniform over the entire cross section. Rather, the pressure is distributed over the cross section according to an ap proximately parabolic curve, the highest pressure being in the center and the lowest pressure at the periphery. Corresponding to this pressure distribution, the upward surge of the stream is greatest in the center and weakest along the outer periphery. This would be unimportant if this pressure distribution did not have an annoying mechanical effect. Particles disposed in the center of the stream are more strongly accelerated than the particles along the outer periphery. They are so-to-speak, shot out of the stream. This problem also was solved by inserts built in at the point where the stream leaves the combustion chamber and enters the treatment chamber. These inserts convert the free jet into a stream without core. But these inserts which are disposed at the points of highest temperature are complicated structural components and are attacked by the treatment gas even when good cooling is provided. The use of highly fire-resistant material is economically limited. Thus, these inserts often require repairs and replacement.

Thus, there resulted the problem of producing a method and an apparatus which would produce with simple means, on one hand, a homogeneous temperature distribution of the gas stream and, on the other hand, would prevent particles from being shot out of the gas stream.

This difficult problem was solved according to the present invention in that the treatment gas stream is produced as a swirling stream within a combustion chamber free of inserts before it passes into the treatment chamber and is introduced into the treatment chamber with this swirling action.

In the system of U.S. Pat. No. 2,435,927 discussed above, there is also produced a central gas stream. Here, too, a helical movement of the treatment gas is desired, but thishelical movement does not start within the combustion chamber. Rather, it begins only in the treatment chamber and only at the point where the particles leave the hot gas stream. The combustion chamber produces a hollowgasstream which encloses the stream of treatment material and which mixes with the helically moved gas only at a later point.

The swirling stream produced in the combustion chamber of the present invention has a substantially homogeneous temperature and pressure distribution with respect to its cross section. Consequently, a combustion chamber which is placed ahead of the gas discharge point and which has a plurality of burners whose gas streams swirl therethrough is no longer necessary. The system becomes simpler and less expensive. Guide elements for forming a coreless stream are eliminated. The swirling stream does not have a core in the axial direction of the stream, where there is an increased upward surge. No particles can shoot out of the center of the stream. Since the particles no: longer move in a straight line during the circulation flow, at least in the upward direction, but on a helical line, the same chamber height extends the treatment path. The expansion is more intensive, and the number of charges per hour can be increased.

Due to the fact that the swirling stream is already produced in the combustion chamber and deflection means before transition into the treatment chamber, as they were required with the burner-equipped combustion chamber constructed of the Carpenter patent, are no longer necessary, and the formation of baked-on crusts is avoided.

In connection with the present invention, the method according to U.S. Pat. No. 2,435,927 has already been discussed. The relationship of the present invention to the expansion process according to U.S. Pat. No. 3,201,099, issued Aug. 17th, 1965 to George Carpenter and entitled Method of Expanding Perlite and Like Materials, will now be discussed.

The treatment stream in the Carpenter process is produced in a combustion chamber which in its lower portion is cylindrical and conically narrowed in its upper portion and which is provided with two inserts, and a hollow cone and a pipe inserted thereinto which has external screw threads and which becomes a conical funnel at its upper end. The funnel forms a kind of adjustable nozzle with its discharge cross section at the transition point from the combustion chamber to the treatment chamber. In the cylindrical portion of the combustion chamber, tangentially directed burners are used to produce a reducing atmosphere. The air required for complete combustion is fed in through the helical threads of the inserted pipe. The hollow cone is provided with tangentially directed outlets somewhat below its head, from which outlets combustion air is introduced into the area between the jacket and the hollow cone. Thus, an intensive turbulence is produced by the tangential introduction of the fuel and by the tangential outlets in the hollow cone, and is produced at the output of the helical threads of the pipe out of the hollow cone. One could, thus, be tempted to assume that this arrangement would also produce a swirling stream into which the material to be expanded is introduced. This is not the case, however. For, in the nozzle defined by the funnel of the pipe at the transition into the treatment chamber, the swirling action is braked if it has occurred at all. A core-free annular stream results as in the above-mentioned known proposal'having guide elements at the transition point from combustion chamber to treatment chamber. If any kind of swirling movement should still be present, which would probably be very little, it would not be enough to carry along the material to be expanded. This actually is not necessary in this known process, because the granules are fed into the treatment chamber, far above the transition point of the gas into the treatment chamber fall a certain distance within the treatment chamber, whereby they are expanded, and are then discharged at the top by the induced draft. They do not perform a circulation flow, but only a somewhat U-shaped path. For this it is necessary that the treatment stream fill the entire chamber cross section. Otherwise, a portion of the granules would fall outside of the gas stream to the bottom of the combustion chamber without being expanded. The important part of the present invention that is, the generation of a swirling stream full of energy which does not fill the chamber cross section cannot be realized with this arrangement. Only when the stream is produced in a combustion chamber free of inserts, is it possible for it to continue its swirling movement in the treatment chamber with sutficient swirling energy, whereby the stream is so formed'that the granules are discharged therefrom and can fall back to the starting point of the stream outside of the stream.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic, partial, side-elevational, crosssectional view of a combustion chamber for producing the swirling gas stream according to the present invention, so that a circulation flow is produced in the swirling stream.

FIG. 2 is a detail of FIG. 1 on a larger scale.

FIG. 3 is a partial, top-plan, cross-sectional view taken generally along line 33 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It should first be noted that the illustrated combustion chamber is only exemplary, and is not requisite under all circumstances. It represents a particularly high-quality combustion chamber.

The combustion chamber 1 is enclosed by a jacket 2 formed of outer walls 3 and 5 and intermediate wall 4. In this way cylindrical hollow chambers are produced between walls 5 and 4 and between walls 4 and 3. These chambers are in communication with one another via a battle zone 6.

The combustion chamber 1 is closed at the bottom by a lowerable bottom portion 8 which bears a suitable burner head 9 with fuel nozzles 10. The construction of the nozzles 10 forms no part of the present invention as nozzles 'of this type are well known in the art in different forms, e. g. as shown in U.S. Pat. No. 2,932,498, issued Apr. 12th, 1960, to R. L. Metcalfe et. al. The nozzles 10 are so directed that the fuel streams emanating therefrom are atomized in the direction toward wall 3 and are mixed with the air, so that burning of the fuel takes place in the air.

The preferred fuel is liquid fuel, especially oil, but a pulverized solid fuel or a gaseous fuel could also be used.

Air comes tangentially out of openings, or slots, 11 and, as will be shown later, they have a swirling motion.

Fuel and air are mixed and form the swirling stream within the combustion chamber 1 to correspond with the number of air outlets l1 distributed on wall 3. Only one of these outlets 11 is illustrated. At the transition point from the combustion chamber 1 to a conical portion 12 of a treatment chamber that is in the zone marked 13 an energy filled swirling gas stream is formed. This energy should be sufficient for granules entering the stream to leave it in the lower portion of the treatment chamber (FIG. 1

The illustrated embodiment shows why it is so important that the combustion chamber 1 does not have any inserts. Each insert portion in the path of the swirling stream would reduce the swirling motion or would remove it altogether. Only when the swirling movement can develop within the combustion chamber free and unhampered, is it assured that the treatment gas stream enters into the treatment chamber with a swirling motion. It is in this zone that the granules to be expanded enter into the gas stream. They are indicated schematically by path 14.

It has already been briefly mentioned that it is a particular feature of combustion chamber 1 that the air enters it with a swirling movement. This may be realized in the following manner.

Air is fed in through pipes 15 which enter tangentially into the outer jacket 5 (see FIG. 3). it is unim portant whether the air is fed in with excess pressure or whether it is sucked in by the induced draft. In any case, no pure tangential streams are formed in the area between the walls 5 and 4, but there instead occurs a helical movement. With this helical movement, the air ascends between walls 5 and 4 and is deflected downwardly in zone 6. The helical movement remains intact and continues during the subsequent downward flow between walls 4 and 3, so that the air enters combustion chamber 1 with a swirling motion. In order to increase this swirling motion, baffles 16 may be provided in this embodiment before openings 1 1.

The swirling stream is, therefore, produced in this embodiment substantially exclusively by the swirling effect of the air introduced to combustion chamber 1. Understandably, the axes of nozzles 10 can also be aligned to produce a swirling movement, but this would mean, in this embodiment, only a reinforcement of the swirling movement of the air.

It should be particularly emphasized that this is a particularly suitable embodiment, but not the only embodiment to carry out the present invention. The advantage lies in the excellent cooling of the walls of the combustion chamber 1 which is constructed from, for example, steel and does not require a heavy ceramic material for its installation or lining. The air ascending in a swirling movement in the space between walls 5 and 3 takes on heat which is transmitted by irradiation to the wall 4. The outer wall 5 remains cool. The heat absorbed in this manner is not lost, but is returned to the combustion chamber.

The portion under highest thermal stress is wall 3. Since the air now flows downwardly between walls 4 and 3 with a swirling movement, wall 3 is intensively cooled. The swirling movement does not permit the formation of a border layer which might develop with a simple downward flow in this area.

A further advantage is that the swirling movement is not produced, as is the usual practice, only by appropriately directed outlets 11, but that it arrives with a swirling motion at these outlets 11. The swirl intensity is correspondingly augmented.

The temperature of the hot gas stream contacting the granules depends on the nature of the granules and of their size. Normally the temperature is between l,l00 und l,200 C. The pressure of the ascending gas stream entering the treat-ment chamber must be high enough so as to carry the granules with it at least over the axial length of the conical part at the bottom of the treatment chamber.

No fixed parameters can be given as they vary dependent on the quantity of the charge, the nature and size of the granules, their moisture content and other variables. It is not difficult, to adapt the formation of the swirling gas stream to the character of the charge to be expanded. I

It will be understood that the above description of the present invention is susceptible to various modific a tions, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

We claim:

1. A method for expending clay granules in a hot gas stream within a treatment chamber, comprising the steps of:

a. forming a hot ascending gas stream in a combustion chamber in the form of an axially streaming, swirling gas stream having a cross section which is less than the largest cross section of the treatment chamber;

b. introducing a charge of granules directly into the hot ascending swirling gas stream in order to carry the granules upwardly in the treatment chamber, to permit the granules to leave the gas stream and return, under the effect of gravity and outside of the gas stream, to the end. of the treatment chamber at which the gas stream enters and thereby to be reintroduced into the ascending gas stream, and recirculating the granules until they are all completely expanded; discontinuing the gas stream when the granules of the charge are completely expanded; and

d. discharging the expanded charge.

2. The method of claim 1, further including the step of providing an insert-free combustion chamber.

3. The method of claim 2, wherein the step of forming a hot gas stream includes the step of producing the swirling gas stream with sufficient energy for the granules entering the stream to leave it in the lowerportion of the treatment chamber due to the centrifugal force exerted on them.

4. Apparatus for expanding clay granules, comprising in combination:

a. a treatment chamber having an axis and in which a charge of granules is introduced to be carried along by an ascending, axially streaming, swirling gas stream; and

b. a combustion chamber having a bottom portion and arranged for providing the axially streaming,

walls to partition same into two chambers which are connected with one another by a baffie zone arranged near the upper portion of said combustion chamber,

the respective walls arranged such that gas flows upward with a helical movement in the first of said chambers and downwardly with a helical movement in the second of said chambers, said slot being arranged such that the downwardly moving gas in the second of said chambers enters the combustion chamber while retaining the helical motion and become the axially streaming, swirling gas stream. 

1. A method for expending clay granules in a hot gas stream within a treatment chamber, comprising the steps of: a. forming a hot ascending gas stream in a combustion chamber in the form of an axially streaming, swirling gas stream having a cross section which is less than the largest cross section of the treatment chamber; b. introducing a charge of granules directly into the hot ascending swirling gas stream in order to carry the granules upwardly in the treatment chamber, to permit the granules to leave the gas stream and return, under the effect of gravity and outside of the gas stream, to the end of the treatment chamber at which the gas stream enters and thereby to be reintroduced into the ascending gas stream, and recirculating the granules until they are all completely expanded; c. discontinuing the gas stream when the granules of the charge are completely expanded; and d. discharging the expanded charge.
 2. The method of claim 1, further including the step of providing an insert-free combustion chamber.
 3. The method of claim 2, wherein the step of forming a hot gas stream includes the step of producing the swirling gas stream with sufficient energy for the granules entering the stream to leave it in the lower portion of the treatment chamber due to the centrifugal force exerted on them.
 4. Apparatus for expanding clay granules, comprising in combination: a. a treatment chamber having an axis and in which a charge of granules is introduced to be carried along by an ascending, axially streaming, swirling gas stream; and b. a combustion chamber having a bottom portion and arranged for providing the axially streaming, swirling gas stream and defining slots near the bottom portion thereof through which gas is tangentially fed into said combustion chamber, and means centrally arranged in the bottom portion of said chamber for atomizing fuel into the stream of gas being tangentially fed through said slots.
 5. The apparatus defined in claim 4, wherein said combustion chamber is defined by a wall portion having two walls arranged such that the gas will flow between said walls on a helical path.
 6. The apparatus defined in claim 5, further including an intermediate wall arranged between said two walls to partition same into two chambers which are connected with one another by a baffle zone arranged near the upper portion of said combustion chamber, the respective walls arranged such that gas flows upward with a helical movement in the first of said chambers and downwardly with a helical movement in the second of said chambers, said slot being arranged such that the downwardly moving gas in the second of said chambers enters the combustion chamber while retaining the helical motion and become the axially streaming, swirling gas stream. 